Chapter 24:
Lipids,
Fatty Acids
& Triglycerides
Lipids
• Organic compounds not soluble in water
Vague, overly general definition
Waxes
Triglycerides
Steroids (inc. cholesterol)
1
Fatty Acids
• Key components of “triglycerides”
• Long-chain carboxylic acids
Typically C10 – C20 chain with –COOH group at end
• Also phosphoric fatty acids (less common)
O
O
HO – C – (CH2)n – CH3
HO – P – (CH2)n – NH3+
Carboxylic Fatty Acid
O–
Phosphoric Fatty Acid
Lauric Acid, CH3(CH2)10COOH
O
HO-C ‒ CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3
- Polar
- Reactive
group
- Nonpolar
- Insoluble in water
- Non-reactive
- Longer chains ⇒ higher melting Temp
(stick to themselves)
• Since not water-soluble, not easily ejected by
body once consumed (not soluble in blood)
• Can be burned by body to generate energy
Fatty Acid + O2 CO2 + H2O + energy
2
Saturated Fatty Acid – no double bonds
CH3(CH2)16 - COOH
COOH
Mono-unsaturated: one double bond in chain
CH3(CH2)7CH=CH(CH2)7 - COOH
COOH
Poly-unsaturated: multiple double bonds
CH3(CH2)4CH=CHCH2CH=CH(CH2)7 - COOH
COOH
Saturated Fatty Acid
COOH
COOH
COOH
Cis-unsaturated fats
COOH
COOH
COOH
Trans-unsaturated fats
COOH
COOH
COOH
COOH
COOH
Cis- fats do not stack
Do not stick together
Lower melting temperature
Less of a health problem
Stack together / Stick together
Higher melting temperature
Clogs arteriers
3
Common Saturated and Unsaturated Fatty Acids
# C’s : Structure
# Db
Bd
Common
Name
Position
of
Double
Bond
Melt
Point
(ºC)
SATURATED FATTY ACIDS
Lauric Acid
12 : 0
CH3(CH2)10COOH
44
Myristic Acid
14 : 0
CH3(CH2)12COOH
54
Palmitic Acid
16 : 0
CH3(CH2)14COOH
63
Stearic Acid
18 : 0
CH3(CH2)16COOH
70
UNSATURATED FATTY ACIDS
Palmitoleic
Acid
16 : 1
CH3(CH2)5CH=CH(CH2)7COOH
cis-9
0
Oleic Acid
18 : 1
CH3(CH2)7CH=CH(CH2)7COOH
cis-9
16
Linoleic Acid
18 : 2
CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH cis-9,12
-5
Triglycerides
• Fatty acids can be burned by body to create energy
… But stored in body as triglycerides
C-OH
C-OH
O
+ 3
C-OH
glycerine
(1,2,3-propanetriol)
HO-C ‒ (CH2)nCH3
triglyceride
fatty acid
O
C ‒ O-C ‒ (CH2)nCH3
O
C ‒ O-C ‒ (CH2)nCH3
O
C ‒ O-C ‒ (CH2)nCH3
+ 3 H2O
4
Esterification Reaction
Acid + alcohol → Ester + water
‒OH group and alcohol swap places
O
O
HO ‒ CCH2CH3
CH3O ‒ CCH2CH3
+ H2O
Ester
+ CH3OH
Esterification Reaction
Acid + alcohol → Ester + water
O
O
HO ‒ CCH2CH3
CH3O ‒ CCH2CH3
+ H2O
Ester
+ CH3OH
O
HO ‒ C ‒ (CH2)nCH3
O
C-O ‒ C ‒ (CH2)nCH3
C-OH
+ C-OH
C-O
- H 2O
C-OH
C-O
2
more
times
Triglyceride
5
Fats and Oils
• Both are triglycerides made up of fatty acids
• Fats: have melting temp’s higher than 25ºC
Are solids at room temperature
• Oils: have melting temp’s less than 25ºC
Are liquids at room temperature
O
C ‒ O-C ‒ (CH2)nCH3
Fat vs. oil
depends on
which fatty
acids are
present
O
C ‒ O-C ‒ (CH2)nCH3
O
C ‒ O-C ‒ (CH2)nCH3
Composition of Common Fats & Oils
Saturated
C12
Lauric
C14
C16
Myristic Palmitic
Unsaturated
C18
Stearic
C18
Oleic
(cis)
C18
Linoleic
(cis,cis)
44
58
63
70
4
-5
Lard
-
1
25
15
50
6
Butter
2
10
25
10
25
5
Human fat
1
3
25
8
46
10
Whale blubber
-
8
12
3
35
10
Corn
-
1
8
4
46
42
Olive
-
1
5
5
83
7
Peanut
-
-
7
5
60
20
Soybean
-
-
7
4
34
53
Melting Temp (C)
Animal Fat
Vegetable Oil
6